1. Field of the Invention
The present invention relates to a method of manufacturing a disc-shaped recording medium including a plurality of recording faces.
2. Description of the Prior Art
The manufacture of, e.g., a single-sided 2-layered type Blu-ray Disc capable of recording with a higher density than a DVD requires a spacer layer onto which recording faces are transferred. In processes of manufacturing this type of optical disc, however, as shown in FIG. 8, in the case of adopting a 2P transfer method for forming a spacer layer 102 between a disc-shaped substrate 101 and a stamper 103, it is required that the stamper 103 be exfoliated after forming the spacer layer 102. The stamper 103 has hitherto been exfoliated after forming a notch between the stamper 103 and the spacer layer 102 by use of a cutter knife 100.
When notched by the cutter knife 100, however, cutting wastage is accumulated and easily left at a tip of the cutter knife 100. This cutting wastage is adhered to the disc-shaped substrate 101 by static electricity generated when exfoliating the stamper 103. The cutting wastage, if left as it is, becomes a defect of the optical disc and therefore needs to be removed. This is time-consuming and leads to an increase in manufacturing costs. Further, the cutter knife is fixed and is therefore incapable of following up with a surface deflection and eccentricity of the disc-shaped substrate, and it often happens that completely-notched portions and incompletely-notched portions are formed. These incompletely-notched portions cause an occurrence of burrs after the exfoliation, which is a factor of decreasing a manufacturing yield of the optical disc.
Moreover, Japanese Patent Application Laid-Open Publication No.2002-197731 discloses an exfoliation method of partly exfoliating a portion between a disc substrate and a dummy disc that are bonded by a bonding agent, and exfoliating the dummy member from the disc substrate by supplying a compressed gas to between the disc substrate and the dummy member which have been partly exfoliated and expanded. This exfoliation method, however, requires equipment, a pipe arrangement, etc. for supplying the compressed gas.